1. Field of the Invention
The present invention relates to a silver halide color photographic material and method of processing the same, particularly light-sensitive materials suitable to a quick and convenient process and a method of processing the same.
2. Description of the Prior Art
Generally, a basic process of processing color photographic materials consists of a color developing step and a desilvering step. In the color developing step, exposed silver halide is reduced by a color developing agent to yield silver and, at the same time, the color developing agent reacts with a color forming agent (a coupler) to produce a dye image. In the subsequent desilvering step, the silver produced in the color developing step is oxidized by an oxidizing agent called a bleaching agent and, then, is dissolved by a complexing agent for silver ion called a fixing agent. By passing through the desilvering step, only the dye image is formed on the color photographic materials.
The above desilvering step is conducted by two baths, i.e., a bleaching bath containing a bleaching agent and a fixing bath containing a fixing agent, or by a single bath of a bleach-fixing solution containing both a bleaching agent and a fixing agent.
In an actual developing process, there are various auxiliary steps to maintain photographic and physical quality of an image or to improve preservability of an image in addition to the above basic steps. For instance, there are a hardner bath, a stop bath, an image stabilization bath and a water washing bath.
Generally, ferricyanide, bichromate, ferric chloride, ferric aminopolycarboxylate complex and persulfate are known as a bleaching agent.
However, ferricyanide and bichromate have a pollution problem due to cyan compounds and hexavalent chromium, and therefore, some special treatment equipments are required to use these. Further, ferric chloride has problems such as formation of iron hydroxide in a water washing step thereafter and generation of stain and, accordingly, has various obstacles in practical use. Persulfate has a disadvantage that its bleaching ability is very weak and bleaching takes very long time. Regarding this point, a method of enhancing the bleaching action using a bleach accelerator together has been proposed. However, this method is difficult to be used because, for instance, there is a regulation about persulfate as a dangerous substance and various special cares are required in storage.
Ferric aminopolycarboxylate complex, particularly ferric ethylendiaminetetraacetate complex or ferric diethylenetriaminepentaacetate complex, has only a little pollution problem and has no problem in storage unlike persulfate and, accordingly, is the most generally used bleaching agent. However, the bleaching ability of ferric aminopolycarboxylate complex is not always sufficient. It may attain the envisaged purpose when low speed silver halide photographic materials which mainly uses a silver chlorobromide emulsion is subjected to a bleaching or bleach-fixing process. However, when high speed color photographic materials which mainly use a silver chlorobromoiodide or iodobromide emulsion and is color sensitized, particularly color reversal photographic materials used for taking photographs using an emulsion of a high silver content or color negative photographic materials used for taking photographs, are processed, disadvantageous such as insufficient desilvering and long bleaching time arise.
For instance, when negative photographic materials used for taking photographs are bleached using a bleaching solution of ferric aminopolycarboxylate, at least 4 minutes are required for bleaching and, in addition, complicated cares should be taken to maintain a bleaching power, such as pH control of the bleaching bath and aeration. Even though these cares are taken, insufficient bleach often takes place in fact.
Further, processing by a fixing bath for at least 3 minutes is required for desilvering following the bleaching step. It is strongly desired to shorter such a long period of time for desilvering.
A bleach-fixing solution containing ferric aminopolycarboxylate complex and thiosulfate in a single bath is known as a means of accelerating the desilvering step as described in German Pat. No. 866,605. However, when ferric aminopolycarboxylate which has a weak oxidizing power (bleaching ability) is combined with thiosulfate which has a reducing ability, the bleaching ability of the former are extremely weakened and it is very difficult to sufficiently desilver color photographic materials used for taking photographs of a high speed and a high silver content. Thus, the above solution cannot be used in practice. Of course, many improvements have been made to solve the above draw backs of such a bleach-fixing solution. For instance, UK Pat. No. 926,569 and Japanese Patent Publication No. 11,854/1978 disclose a method of adding iodides and bromides. Japanese Patent Publication (unexamined) No. 95834/1973 discloses a method of incorporating a high concentration of ferric aminopolycarboxylate complex salt using triethanolamine. However, these methods attain merely insufficient effects and cannot be used for practical purpose.
Further, beside the insufficient desilvering ability, a bleach-fixing solution has a serious draw back that it reduces cyan dye formed in color development into leuco dye, which results in deteriorated color reproduction. It is known that this draw back can be improved by raising a pH of the bleach-fixing solution as described in U.S. Pat. No. 3,773,510. However, to raise a pH further weakens the bleaching ability on the contrary and, therefore, this cannot be practically used. U.S. Pat. No. 3,189,452 discloses a method where leuco dye is oxidized back to cyan dye by a ferricyanide bleaching solution after bleach-fixing. However, the use of ferricyanide has the aforesaid pollution problem. Further, even if bleaching is conducted after a bleach-fixing step, the effect of decreasing an amount of the remaining silver is almost not attained.
As another method for raising the bleaching ability of ferric aminopolycarboxylate complex, it has been proposed to add various bleaching accelerators to a bleaching bath, a bleach-fixing bath or a bath preceding these.
For instance, there can be mentioned various mercapto compounds described in U.S. Pat. No. 3,893,858, UK Pat. No. 1,138,842 and Japanese Patent Publication (unexamined) No. 141623/1978, compounds having a disulfide bond described in Japanese Patent Publication (unexamined) No. 95630/1978, thiazolidine derivatives described in Japanese Patent Publication No. 9854/1978, isothiourea derivatives described in Japanese Patent Publication (unexamined) No. 94927/1978, thiourea derivatives described in Japanese Patent Publication No. 8506/1970 and Japanese Patent Publication No. 26586/1974, thioamide compounds described in Japanese Patent Publication (unexamined) No. 42349/1974, and dithiocarbamates described in Japanese Patent Publication (unexamined) No. 26506/1980.
Some of these bleaching accelerators surely show the bleaching acceleration effect. However, their effects not always sufficient and shortening of the process time has not yet been successfully attained only by these techniques.